Retrieving catchment information is done in two steps: first you choose the catchment outlet and preview its boundary, then, when you are satisfied with your selection you may opt to purchase the catchment descriptors and rainfall data.
Step 1: defining your catchment boundary - preview mode
- Choose a location on the map and zoom in a little. It might be helpful turning on the Drainage network layer in the Map layers menu.
- Right click on or near the location you are interested in and select Catchment boundary. The point you click will snap to the nearest section of the drainage network so don’t worry if you miss the drainage network line slightly.
- Following a brief pause (larger catchments may take longer to calculate), the catchment boundary will appear.
To see the catchment at the optimal magnification, click the green "Fit screen" button (screen left).
The orange marker identifies the exact catchment outlet. The green cross shows the nearest 1 kilometre grid post, and the roundel in the centre of the catchment marks its centroid. Need a reminder? Hover your mouse over these markers and a label will pop up.
At any point, you can save a screenshot of the map, including the catchment preview, using the camera icon in the blue toolbar, screen right.
Repeat Step 1, examining its area, boundary and its position relative to the drainage network and underlying OS maps, until you are happy with your selection.
Step 2: Purchasing your catchment
To acquire detailed information about your catchment, you must purchase it using your account credits.
To do this, you will need to:
- have registered for a user Account,
- be logged in to your account, and
- have purchased Credits for your account.
With your catchment in preview mode, click on the "Buy now" button in the catchment menu.
A confirmation window will appear: in there you can optionally rename the catchment and/or add a tag. A tag is a label or code you could use to group a set of catchments related to a single project for instance.
Once you purchase the catchment, the left side of the screen will refresh to show the catchment/point information.
Purchased catchments and points remain associated with your account granting you perpetual access to the data.
Step 3: Viewing and exporting your catchment data
To display purchased catchments on the map, toggle the Purchased Catchments and Org-purchased Catchments switches in the Map layers menu. Catchments will appear in the map as green icons. ("Org-purchased catchments" are ones bought by colleagues within a joint organisational account.) Click on a catchment's map pin and then its name to display its details.
You can also view a list of previously purchased catchments in the Data Management window, using the three lines icon in the blue tool bar, screen right.
Exporting catchment descriptors, rainfall and boundary polygons
Click on the green "Export" button to export catchment data in the .XML and .CSV formats. The XML format includes a full set of catchment descriptors and FEH22 and FEH13 rainfall for use in tools such as ReFH2 (v3.3+) and WINFAP 5+. The legacy exports includes CSV, CD3 and XML formats that do not contain a complete set of descriptors and rainfall data for legacy applications.
You can also export an ESRI shapefile of the catchment boundary.
DDF rainfall modelling window
You can perform DDF calculations for the selected catchment as well as for the 1km grid cell closest to the catchment outlet, by clicking on the blue "Rainfall" button to access DDF rainfall window.